supplement support/suggestion?

Currently working out using the P90X workout routine. Completed the ninty days according to program and have a balanced diet. Taking Muscle Milk before and after workout and saw increased definition but also lost about 12-15 lbs. I can not afford a gym membership so I am doing the p90x routine again but cutting out 2 days of cardio. I want to gain muscle mass, should I take creatine also?